1. The Field of the Invention
The present invention is a continuation-in-part of U.S. application Ser. No. 09/767,384 filed Jan. 23, 2001 now U.S. Pat. No. 6,485,709 and is directed to a dental bleaching gel composition having a long shelf life for use with an activator for a bleaching gel to cause accelerated bleaching action upon a tooth surface over a relatively short time period for cosmetically whitening the tooth and/or for the treatment of stains or discolorations on the teeth.
2. Relevant Technology
Conventional bleaching formulas containing a peroxide-bleaching agent such as hydrogen peroxide run the risk of poor shelf life unless the formulation includes a stabilizer for the bleaching agent. The stabilizer functions to inhibit the breakdown of the peroxide bleaching agent by slowing down the dissociation of the peroxide thereby prolonging its potency over a longer time period. Although shelf life is extended by slowing down the bleaching action the effectiveness of the bleaching composition to whiten teeth is substantially reduced. This, in turn, necessitates repeated applications to achieve a cumulative effect and may require as many as ten applications or more to visually notice any change particularly with low concentration peroxide formulations. Professional treatment on the other hand, generally performed in the dental office, utilizes a high concentration of peroxide bleaching agent of up to 35 wt % of the formulation. Although this is more effective than that of lower peroxide formulations the higher concentration of peroxide requires a proportionally higher concentration of stabilizer to satisfy the shelf life requirements and, as such, still relies on numerous repeated office visits or on lengthy home bleaching treatments to ultimately cause a sufficient clinically effective cumulative effect satisfactory to the patient. In the United States a peroxide bleaching agent formulation must have a shelf life of at least six months at room temperature. Accordingly, all conventional in-office-bleaching formulations presently depend upon lengthy repeated office visits of over two and more to produce whitening satisfactory to a patient. The need for so many applications and/or visits is most undesirable to the patient and uneconomical to a professional practitioner, and as such, most dentists prefer to utilize home bleaching methods.
In-office bleaching compositions are presently categorized as being either a “one-part” or “two-part” system. The distinction is based upon whether all of the components of the bleaching composition are self-contained in a desired pre-mixed proportion or if the active ingredients are isolated and need to be mixed and proportioned before use. In the “two-part” system the components which would otherwise interact with the peroxide bleaching agent are physically separated from one another. The “one-part” system making is much more attractive based upon convenience of application and in sharp contrast to the “two-part” system which is associated with the prior art requirement of both mixing and proportioning the isolated components prior to use. In fact a “two-part” system which relies upon using an aqueous solution for the bleaching composition is also subject to dangerous splattering. Another serious problem with the two part systems of prior art is that the concentration of the peroxide is reduced by 50% when a 1:1 ratio is mixed together. However, in reality, the distinction between a “one-part” and “two-part” system has no significance clinically or upon the end result. Accordingly, what should be of concern is the ability to independently control the activity of the peroxide bleaching agent to minimize the need for repeated applications and or office visits while at the same time achieving extended shelf life.
The present invention is directed to a bleaching composition in the form of a gel for use with an activator which combines the features of both the “one-part” system and the “two-part” system for providing enhanced and independent control over the rate of activity of the peroxide bleaching agent to whiten teeth without affecting shelf life. Moreover the bleaching composition of the present invention permits an FD & C (“Federal Drug and Cosmetic”) approved dye to be combined together with a peroxide bleaching agent in the bleaching composition so that a visual indication of the bleaching material in contrast to the tooth and gingiva is possible thereby providing greater control and safety in the bleaching procedure. The bleaching action and rate of activity of the peroxide bleaching agent is controlled by the activator system which is simultaneously applied to the tooth or teeth to be bleached. Commercially available bleaching gels cannot tolerate an FD & C approved dye together with the bleaching agent particularly at higher concentrations of bleaching agent because the dye would be bleached. The peroxide bleaching agent should preferably be in a concentration of at least about 15 wt %.
The bleaching composition of the present invention is a gel formulation, which is used in conjunction with an activator system which gives the user and professional practitioner the look, feel and handling characteristics of a “one part” system in that no mixing and proportioning of any ingredients is involved. The bleaching gel of the present invention provides significant control over the bleaching operation both in terms of the rate of bleaching and the visual color indication due to the presence of an FD & C approved dye together with the bleaching agent and most important provides significant reduction in the number of office visits necessary because of the high rate of bleaching action. The bleaching action is controlled by the activator system, which accelerates the dissociation of the peroxide bleaching agent into hydroxyl and perhydroxyl free radicals to provide quick and highly efficient whitening of the tooth or teeth surfaces under treatment. Moreover, in accordance with the present invention since the activation of the peroxide bleaching agent occurs essentially simultaneously with the direct application of the bleaching gel to the tooth or teeth surfaces to be bleached a simulated “one-part” system is achieved with the convenience of use of the “one-part” system and the attributes of the “two-part” system.